Qt - Powerful, flexible and easy to use, Qt will help you not only meet your tight deadline, but also reduce the maintainable code by an astonishing percentage.
JavaScript - Lightweight, interpreted, object-oriented language with first-class functions
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Allegro - Allegro 4 and Allegro 5 are cross-platform, libraries mainly aimed at video game and multimedia...
wxWidgets - wxWidgets: Cross-Platform GUI Library
Uno Platform - Build Mobile, Desktop and WebAssembly apps with C# and XAML.